Device for deviating a pencil of light rays



March 14, 1939. o. EPF'ENSTEIN 2,150,544

DEVICE FOR DEVIATING A PENCIL OF LIGHT RAYS Filed Aug. 16, 1938 pushing body Patented Mar. 14, 1939 PATENT OFFICE DEVICE FOR DEVIATING LIGHT Otto Eppenstein, Jena,

mesne assignments, to

A PENCIL OF RAYS Germany, assignor, .by Bausch & Lomb Optical Company, Rochester, N. Y., a corporation of New York Application August 16, 1938, Serial No.

In Germany September 9, 1937 2 Claims.

This application has been filed in Germany- September 9, 1937;

Small angles are frequently measured by means of optical instruments having 'a system of wedge-shaped prisms of continuously variable deviation. The invention concerns that constructional form of such systems which is known by the name of rotating-wedge compensator and composed of two deviating prisms rotatable in opposite senses about a common axis. When these two prisms have a definite reciprocal position, the resulting deviation is zero, because the prisms have the same angles of refraction. The greatest resulting deviation corresponds to twice the deviation of a single prism. If 6 be the deviation to which this prism submits a pencil of light rays incident at approximately right angles, 6 the deviation due'tothe entire system, and o the angle between the refracting edges of the two prisms, the following equation is obtained:

The resulting deviation is, accordingly, proportional to the function of. the cosine of the half angle between the retracting edges. This fact entails, however, a considerable disadvantage of the rotating-wedge compensator, since the resulting deviation is very often required to change in proportion to the mechanical displacements determining it.

This disadvantage can be avoided by proceeding from the idea to make the deviation 6 proportional to the change in the position of a mechanical element rotating the two prisms, which is possible, according to the invention, by providing the rotating-wedge compensator with two stops which include the same angles with the line bisecting the angle between the two refracting edges and are equidistant from the axis of rotation and fixed to the prisms, and with a which is displaceable parallel to the said bisecting line and touches the two stops with a surface at right angles to the bisecting line. By providing that the distance of the stops from the axis of rotation can be changed, the additional advantage is obtained thatthe ratio of transmission between-the pushing body and the prism system can be varied without the desired proportionality of the displacements being interfered with.

In the accompanying drawing, which illustrates the invention, Figure 1 is the top view of a constructional example and Figure 2 a section through the line A-A in Figure 1.

0 E 6 26 cos 2 To an aperture (1 in a base plate b is screwed a compensator tube 0 in which are rotatably disposed the mounts d of two equal deviating prisms e in the form of wedges. arm I extending radially through an opening 9 of the tube 0. A sleeve 71. having a slit 1' is fixed to the arm f by means of a clamping screw k. The sleeve h terminates in a fork Z in which a ring m is rotatable on balls 12 about a bolt 0 parallel to the axis of rotation of the prisms e. The plate I) has two rods p which are parallel to the line bisecting the angle between the two arms 1 and constitute guides for slides q carrying a pushing body r displaceable parallel to the bisecting line. This pushing body? is operated by a threaded spindle s and provided with parts t the surfaces '11. of which lie in a plane at right angles to the bisecting line. The bolts 0 are connected to the body r by tension springs 12.

If a: be the effective length of the arms 1, viz. the distance of the axes of the bolts 0 from the axis of rotation of the prisms, and y the distance of the plane at right angles to the bisecting line and containing the axes of the bolts 0 cos By introducing this magnitude into the Equation (1), there is obtained the resulting deviation 6 being, accordingly, proportional to that position of the pushing body 1' which is represented by the distance y and inversely proportional to the eifective length of the arms I.

To rotations of the spindle s about the same angles correspond equal variations of the deviations efiected by the rotating-wedge compensator, and the ratio of transmission between the I ing fast with one of said glass wedges, two rollers, each of said rollers being rotatable about an axis in one of said arms, the axes of rotation of said rollers being parallel to and equidistant from Each mount it has an the axis ofrotation of said wedges, the two planes containing the axis of rotation of said wedges and the axes of rotation of said rfiilers including equal and opposite angles with the refracting edges of said wedges, respectively, a pushing body disposed on said housing, and

means for displacing said pushing body parallel.

to a straight line at right angles to the axis of rotation of said wedges and parallel to the plane bisecting the angle included 1 zthe planes determined by the axes of rotation of said rollers and the axis of rotation of said wedges, said rollers being in contact with a surface of said pushing body, said surface being plane and at 

